UVB better than Vit D supplements for pet reptiles March 2010
Comp Biochem Physiol B Biochem Mol Biol. 2010 Mar 4. [Epub ahead of print]
Effects of vitamin D(3) supplementation and UVb exposure on the growth and plasma concentration of vitamin D(3) metabolites in juvenile bearded dragons (Pogona vitticeps).
Oonincx DG, Stevens Y, van den Borne JJ, van Leeuwen JP, Hendriks WH.
Animal Nutrition Group, Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands.
The effectiveness of dietary vitamin D(3) and UVb exposure on plasma vitamin D metabolites in growing bearded dragons (Pogona vitticeps) was studied. A total of 84 (40 males and 44 females) newly hatched bearded dragons were allocated to six levels of oral vitamin D(3) supplementation (0 to 400%) or six UVb exposure times (2 to 12h). At 3 and 6months of age, blood samples were obtained from each animal and analysed for 25(OH)D(3) and 1,25(OH)(2)D(3). At 3months of age, plasma concentrations of 25(OH)D(3) did not increase with increasing vitamin D(3) supplementation unlike the 1,25(OH)(2)D(3). At 6months of age, plasma concentrations of both 25(OH)D(3) and 1,25(OH)(2)D(3) increased with increasing vitamin D(3) supplementation. 
Plasma concentrations in UVb-exposed animals were 18 times higher for 25(OH)D(3) (178.4+/-9.0 vs. 9.9+/-1.3nmol/L) and 5.3 times higher for 1,25(OH)(2)D(3) (1.205+/-0.100 vs. 0.229+/-0.025nmol/L) than in vitamin D(3) supplemented animals at 6months of age. 
This study shows that 2h of UVb exposure enables adequate physiological concentrations of plasma vitamin D metabolites to be maintained in growing bearded dragons. 
Oral supplementation of vitamin D(3) is ineffective in raising plasma concentrations of 25(OH)D(3) and 1,25(OH)(2)D(3) to concentrations observed in UVb-exposed animals. Copyright © 2010. Published by Elsevier Inc.
PMID: 20206712 [PubMed - as supplied by publisher]